Will it work? yes...will it work well is another story.
The ipod touch has a better DAC and probably on-hand storage.
Is your cousin including the SD card? an if so is the space on the SD card enough for your son? (as sd card increases the additional cost)
Nest I would borrow it from your cousin and load up a few song on it and see if your son says its ok. (cause as I said before the DAC on the Evo is subpar, there are Android devices which much much much better DACs, but hey if your son cant tell the difference
lol)
Me personally I used my TP2 as a music device and was ok with it, until I got my Epic(has one of the best DACs)...the difference in sound quality was out of this world >.>
Then again for the same cost you can ebay a fascinate(2gb built in) and a little more a vibrant/captivate(16gb built in) and you will have better sound quality.(just make sure to install voodoo sound)